1. Field of the Invention
The present invention relates to a liquid discharging head for discharging liquid by generating bubbles by virtue of thermal energy being acted on the liquid and a liquid discharging apparatus using the liquid head. The present invention also relates to a novel liquid discharging method associated with displacement of a removable member and bubble growth, and a liquid discharging head and a liquid discharging apparatus for performing thereof.
The present invention is applicable to such apparatus as a printer, a copier, a facsimile having a communication system, a word processor having a printer, or the like for recording on a recording medium such as paper, yarn, fiber, woven fabric, leather, metal, plastic, glass, wood, ceramic, or the like, and further to an industrial recording apparatus compositely combined with various kinds of processing apparatuses. In this invention, xe2x80x9crecordingxe2x80x9d means not only providing a meaningful image of a character or a picture onto a recording medium but also providing a meaningless image such as a pattern or the like.
2. Related Background Art
Conventionally, an ink jet recording method for producing an image first by providing energy such as heat or the like to ink to cause a state change associated with abrupt volume change and generation of bubbles, and then discharging the ink from a discharging port by means of active force originated from the state change to adhere the ink onto the recording medium, or so-called a bubble jet recording method. To the bubble jet recording method, a discharging port for discharging ink, an ink flow path communicating with the discharging port, and an electrothermal converting element as a means for generating energy for discharging ink disposed in the ink flow path are provided, as disclosed in official gazettes such as the specification of U.S. Pat. No. 4,723,129 and the like.
According to such recording method, as a high quality image can be recorded in high speed and with reduced noise, and a discharging port for discharging ink can be arranged in high density on a recording head by the method, the method has a plenty of advantages such that a high resolution recorded image can be produced by a compact apparatus, and even a color image can be obtained with ease. Therefore, in recent years, the bubble jet recording method has been used in a multiplicity of office apparatuses such as printers, copiers, facsimiles and the like, and further even in industrial systems such as textile printing apparatuses and the like.
With the spread use of the bubble jet technique in a variety of products, a variety of demand such as follows has further been increasingly made in recent years. As an example, optimization of a heating element such as adjustment of the thickness of a protective film is consideration to the demand for improvement in energy efficiency. This method has an advantage to improve conductive efficiency of generated heat into liquid. Further, in order to obtain a high quality image, a driving condition for providing a liquid discharging method and the like in which ink discharging speed is fast, and which can discharge ink attributable to stabilized bubble generation in a good condition have been proposed, and in order to obtain a liquid discharging head which is fast in speed in refilling discharged liquid into a liquid flow path, from a stand point of high speed record, an apparatus having improved liquid flow path shape has been proposed.
Among the flow path shape, the flow path construction and the head manufacturing method described in Japanese Patent Application Laid-Open No. 63-199972 and the like are inventions taking notice of a back wave (pressure toward the direction reverse to the direction toward the discharging port, or pressure toward a liquid chamber) which is generated in association with the generation of bubbles. The back wave is known as energy loss, as the energy is not directed to the discharging direction. A head disclosed in Japanese Patent Application Laid-Open No. 63-199972 has a valve located apart from a bubbling region of bubbles produced by a heating element and opposite to a discharging port relative to the heating element. The valve has an initial position as if stuck to a ceiling of the flow path because of the manufacturing method by use of plate material or the like, and hangs down into the flow path in association with generation of the bubbles. The invention discloses that energy loss can be controlled when a part of the above described back wave is controlled by the valve.
However, in the construction, as can be seen if behavior in the flow path before and after generation of bubbles in the flow path which retains liquid to be discharged, partial inhibition of the back wave by a valve can be understood not necessarily practical for liquid discharging. Originally, the back wave itself is not directly related with the liquid discharging. Therefore, even if a part of the back wave is inhibited, the liquid discharging cannot be greatly influenced.
Further, in order to improve ink refilling and obtain a head which is excelled in frequency responsibility, a head of a structure in which heater neighborhood of a nozzle is communicated with a subordinate flow path has conventionally been proposed. When refilling ink, ink is refilled as well from the subordinate flow path into the nozzle to reduce refilling time. However, the head of the structure has a fear that reduction in discharging efficiency may be caused, as a part of the discharging force generated at the time of bubbling escapes to the subordinate flow path.
A major object of the present invention is to improve fundamental discharging characteristic in a method for producing bubbles (more particularly, bubbles associated with film boiling) in a liquid flow path to discharge liquid, to such a level unthinkable and unpredictable from the conventional standpoint.
Some of the inventors of the present invention previously came back to principles of liquid droplet discharging, and devotedly studied to provide a novel liquid droplet discharging method using bubbles which had conventionally been unobtainable, and a head and the like to be used therefor. More particularly, a first technical analysis which is originated from operation of a movable member in a liquid flow path such as analysis of the principle of structure of a movable member in a flow path, and a second technical analysis which is originated from the principle related to liquid droplet discharging by bubbles, and further a third technical analysis which is originated from bubble producing region of a heating member for producing bubbles have been performed.
As a result of these analyses, a completely novel technique for positively controlling the bubbles has come to be established by disposing the movable member facing to the heating member or the bubble generating region. Another feature of the present invention is, based on knowledge that use of downstream growth component of a bubble is the greatest contributing factor in significantly improving the discharging characteristic, if energy given to the discharging volume by the bubbles per se is considered, to efficiently convert the downstream growth component of the bubbles toward the discharging direction. By the conversion, improvement in the discharging efficiency and the discharging speed can be realized.
The present invention is to provide a novel discharging method and a novel discharging principle which further improve the above described epoch-making discharging principle. In other words, the present invention seeks after a discharging principle which enables further improvement in the discharging efficiency and refilling properties, by considering relation between the displacement of a free end of the movable member and the growth of bubbles obtained from the bubble generating region, and further, arrangement of the movable member and a structural element of the liquid flow path.
One of the objects of the present invention is to provide a liquid discharging head, a liquid discharging apparatus, and a liquid discharging method with improved discharging efficiency and liquid refilling properties, by considering arrangement of the movable members and a structural element of the liquid flow path.
Another object of the present invention is to provide a liquid discharging head, a liquid discharging apparatus, and a liquid discharging method with improved refilling frequency and printing speed, by inhibiting the inertia to work in a direction reverse to the liquid feeding direction due to the back wave by the valve mechanism of the movable member, and by reducing retreat volume of meniscus.
A further object of the present invention is to provide a liquid discharging head, a liquid discharging apparatus, and a liquid discharging method with improved discharging efficiency by making the removable member quickly arrive at a proper displacement position, by reducing resistance from the liquid flow path to the predetermined displacement position of the movable member, when the valve mechanism of the movable member is activated by generation of the bubbles.
A further object of the present invention is to provide a liquid discharging head, a liquid discharging apparatus, and a liquid discharging method which are capable of liquid discharging in good condition by greatly reducing heat accumulation in the liquid on the heating member and by reducing residual bubbles on the heating member.
A further object of the present invention is to provide a liquid discharging head, a liquid discharging apparatus, and a liquid discharging method which are capable of solving mechanical characteristic problems associated with difference of the materials of each composing part of the liquid discharging head.
A further object of the present invention is to provide a liquid discharging head, a liquid discharging apparatus, and a liquid discharging method which are capable of making the liquid discharging head compact by solving problems associated with assembling of each composing parts of the liquid discharging head, and by achieving a high density arrangement of the heating member on an element substrate.
A further object of the present invention is to provide a liquid discharging head comprising a discharging port for discharging liquid, a liquid flow path communicated with the discharging port, a bubble generating region for causing the liquid to generate a bubble, and a movable member having provided thereon a free end disposed facing to the bubble generating region, and on the downstream of the liquid flow path directed toward the discharging port, wherein at least when the moving member is in stationary state, a side of the liquid flow path corresponding to the bubble generating region is substantially composed of all with a wall face said wall face existing at a side of said free end of said movable member when said movable member is at a maximum displacement state, and common communicating space commonly communicating the liquid flow path with a neighboring liquid flow path is provided in the upward of a movable section of the movable member.
A still further object of the present invention is to provide a liquid discharging method using a liquid discharging head, having a discharging port for discharging liquid, a liquid flow path communicated with the discharging port, a bubble generating region for causing liquid to generate a bubble, and a movable member disposed facing to the bubble generating region and having provided thereon a free end on the downstream of the liquid flow path directed toward the discharging port; comprising a liquid discharging process for discharging liquid by a side of the liquid flow path, corresponding to the bubble generating region which is at least substantially composed of all with a wall face, a side portion of said free end of said movable member when said movable member is at a maximum displacement state and the movable member, such that growth of a bubble in the bubble generating region is inhibited to be directed toward the discharging port, and a liquid feeding process for feeding liquid, after bubble shrinkage being started, from common communicating space which commonly communicates the liquid flow path with a liquid flow path neighboring to the liquid flow path, arranged in the upward of a movable section of the movable member, toward the discharging port.
According to the present invention, by effectively leading expansion of the downstream portion of a bubble, generated in the bubble generating region, and travel of the liquid associated therewith toward the direction of the discharging port, discharging efficiency can be improved. Further, expansion of the upstream portion of a bubble and travel of the liquid associated therewith toward the upstream can be prevented or inhibited by the movable member, a side wall along displacement of the movable member, and an upper wall in the direction of displacement. Further, when the bubble shrinks and the liquid is refilled in the direction of discharging, high speed refilling is made possible from a low flow resistance region, which is lacking an upper wall, adjacent to a side wall, associated with return of the movable member. Further, by the side wall, side escape of the bubble and discharging pressure to the neighboring liquid flow path can be prevented, enabling efficient discharging of the liquid in the vicinity of the discharging port, thus the discharging efficiency can be improved.
In this way, stabilized growth of the bubble and stabilized production of the liquid droplet can be achieved, enabling high speed and high quality recording in high responsibility by a high speed liquid droplet. Further, synergistic effect between the growing bubble and the movable member which is displaced thereby can be obtained, enabling the liquid in the vicinity of the discharging port to be efficiently discharged, thus the discharging efficiency can be improved.
Further, according to the present invention, when a movable member travels to a predetermined displacement position by growth of the bubble, resistance which the movable member receives from a liquid flow path is reduced to enable the movable member quickly arrive at a proper displacement position, thus the discharging efficiency can be improved.
According to the present invention, by having a fulcrum of a movable member existed in a common liquid chamber, refilling properties of liquid can be improved.
According to the present invention, even when a liquid discharging apparatus is left standing at the low temperature or in the low humidity, the liquid discharging apparatus is prevented from becoming discharging-unable, and even if the liquid discharging apparatus becomes discharging-unable, the liquid discharging apparatus has an advantage of being recovered to the normal state on the spot by a simple recovery process such as preliminary discharging or absorption recovery. By the recovery process, time required for recovery can be reduced, and liquid loss can be reduced, thus running cost can significantly be reduced.
In the present invention, if silicon based material is used as material for each composing part, ink resistance can be improved, and problems of mechanical characteristic associated with difference in linear expansion coefficient of each composing part can be solved.
In the present invention, if each composing element is incorporated in a film forming process, problems of mechanical characteristic and problems associated with assembly can be solved, and further achieving high density arrangement of heating member on the element substrate, enabling compactization of a liquid discharging head.
Meantime, xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d used in the description of the present invention represent expressions regarding flow direction of liquid from feeding source of the liquid toward the discharging port via the bubble generating region (or a movable member). Further, xe2x80x9cdownstream sidexe2x80x9d regarding the bubble itself mainly represents a portion of the bubbles on the side of the discharging port which is said to directly act on discharging of liquid droplet. More particularly, the bubble generated in the downstream relative to the above stated flow direction with respect to the center of the bubble, or in the downstream region from the center of the area of the heating members is meant.
Further, xe2x80x9csubstantially closedxe2x80x9d used in the description of the present invention means, when a bubble grows, the bubble is in a state such that the bubble is unable to pass through a slit around the movable member prior to the displacement of the movable member.
Further, xe2x80x9cseparation wallxe2x80x9d used in the description of the present invention means, in a broad sense, a wall (a movable member may be included) which intervenes such that the bubble generating region is separated from a region directly communicated with the discharging port, and in a narrow sense, a matter which separates a flow path including the bubble generating region from a liquid flow path directly communicated with the discharging port to prevent mixing of liquids being in respective regions.
Further, xe2x80x9cbubble generating regionxe2x80x9d used in the description of the present invention represents a region where a bubble, generated between a substrate having means for causing the liquid to generate a bubble and a movable member can exist, and when a bubble generating means is a heating member, the region occupies a range slightly larger than the area of the heating member under the normal driving condition applicable to the products. Besides, displacement of the movable member associated with expansion of the bubble enlarges the bubble generating region, and the region where the bubble has existed can finally be defined as the bubble generating region.
The other objects of the present invention will be understood from the following description.